Electric furnace and stock feeding means therefor



Dec,'18, 1951 H. A. sTRlcKLAND, .1R

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR 7 Sheets-Sheet l Filed Jan. 16, 1948 lu... HMI

ATTORNEY Dec. 18, 1951 H. A. STRICKLAND, .1R

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR 7 Sheets-Sheet 2 Filed Jan. 16, 1948 .TOM

INVENTOR w LHQYOMQQ. Striddcmcllr:

WC1/vvv 50( OW ATTORNEY Dec. 18, 1951 H. A. STRICKLAND, JR

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR m@ Ill ATTORNEY 'INVENTOR Harold JQ Sicldandjr @m l mi y 7 Sheets-Sheet 3 WOW/@LL PC, @um

l l J l l I l l l I l l l I l l .ll

7 sheets-sheet 4 INVENTOR ATTORNEY Dec. 18, 1951 H. A. STRICKLAND, JR

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR Filed Jan. 16, 1948 www Hm Dec. 18, 1951 H. A. sTRlcKLAND, JR 1 2,578,760

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR Fiied Jan. 1e, 194s 7 sheets-sheet 5 5 .6 w t 54 j Harold H S Uiddandjz ATTORNEY Dec. 18, 1951 H. A. sTRlcKLAND, JR

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR '7 Sheeis-Sheet 6 Filed Jan. 16, 1948 'INVENTR ATTORNEY Dec. 18, 1951 H. A. STRICKLAND, .JR 2,578,750

ELECTRIC FURNACE AND STOCK FEEDING MEANS THEREFOR Filed Jan. 16, 1948 '7 Sheets-Sheet 7 WATER SHUT OFP 50i DELAY TIMER D. z o u INVENTOR. "Harold 43. Srichlandjr.

ATTORNEY Patented Dec. I8, 1951 UNITED STATES PATENT OFFICE ELECTRIC FURNACE AND STOCK FEEDIN G MEANS THEREFOR Harold A. Strickland, Jr., Detroit, Mich., assigner, by mesne assignments, to The Ohio Crankshaft Company, Cleveland, Ohio, a. corporation of Ohio Application January 16, 1948, Serial No. 2,614

3 Claims. (Cl. 21S-47) l 2 This invention relates to heating furnaces and and related feeding apparatus embodying the stock feeding means therefor, particularly to present invention; through-feed or continuous furnaces of the high Figure 2 is a left side elevation of the same apfrequency induction heating type disclosed in the paratus, with the doors in place and with the patent to Strickland 2,325,638 of August 3, 1943,I hood in raised position;

and has for an object the provision of improve- Figure 3 is a top plan view, with the hoods ments :in-this art. closed and with the soaking chamber hood swung One of the particular objects of the invenout to one side; tion is to provide improved heat dissipating Figure 4 is an enlarged partial vertical section meansV for one or more coils or a portion of of the rear or discharge end of the furnace, the one or more coils which are subject to high tem- Section being taken on the line 4-4 of Fig. 3 but perature conditions, as from a workpiece after it with the soaking chamber hood returned to its has been heated. normal operating position;

Another object of the invention is the provision Figure 5 is a transverse vertical section and eleof a high-frequency, induction-heating furnace VatlOH taken 011 the line 5-5 0f Fgl; which is relatively simple but rugged in ccnstruc- Figure 6 is a partial vertical transverse section tion and which will give a maximum amount of taken 0n the line 6--6 0f Fg2 service with a minimum amount of maintenance IFigure '7 is a left side elevation and section taken at a relatively high electrical emciency- 011 the line l-l 0f Fg- 6;

In Order to provide a full understanding 0f 20 Figure 8 is an inclined longitudinal section the complete machine, there will be described and eleVa'OIl, laken abOllt 011 the line 8-3 0f herein certain time sequence controls, certain Fig. 5; stock feed and heating interlocks, certain se- Figure 9 is a transverse vertical section taken lective controls for operating the feed mechanism on the line 9 9 of Fig. 8; withoutthe heating means, certain selective means Figure 10 is a perspective view of the cooled for reapplying the heat after a shut-down either stock guide rails and related parts; in stages or all at once, certain means providing Figure 11 is a schematic View and wiring diacontrolled after-flow of cooling fiuid for a limited gram; and time after a shut-down, certain time control Figure 12 jgacycle diagranr means for matching Work Operations and shutting 3() The furnace hel-ein Shown comprises a Supdown operations if not effected inapredetermined porting frame or mu1tip1e unit cabinet lg with period of time. These features, which are diS- three units Ia, Ib and Ic, associated with a closed but not claimed herein, form the subject skeleton framework II which is welded or riveted matter of other applications 0f applicant and up from angle, channel or other standard pieces Dona-ld W. Riddell O1' 0f applicant 01' Riddell 35 of metal as needed for the number of heating units alone; namely, Serial No. 2,613 filed January 16, to be used. Mounted above and in association re- 1948, now Patent No. 2,563,833, and entitled spectively with each of the cabinets are a like WOlkDeCe Support and Guide OI Indilcerinumber of electric induction heating coils I2, HeatingFurnaces in the name of the present aphere distinguished as I2a, I2b and I2c. From Dlicant; Serial No. 2,615 filed January 16, 1948, 4o front to rear end, or right to left in Fig. 2, these 110W Patent N0. 2,572,073, and entitled Electric heating coils are also referred to as #L #2 and Furnace. and Feeding Means and the Controls #3. Preferably high frequency heating current Therefor in the name of Harold A. Strickland, Jr., is used for heating. and Donald W. Riddell and Serial No. 790,154 led In the upper part of each cabinet there are December 6, 1947, and entitled Heating and Workplaced a number of capacitors I '3 and in thelower Handling Apparatus in the name of Harold A. part of each cabinet there are placed suitable Strickland, Jr., and Donald W. Riddell. contactors I4. There are two contactors for each The above and other objects and advantages coil and one of these is shown in side elevation in of the invention will be apparent from the follow- Fig. 5.

ing description of an exemplary embodiment of Suitable bus bars and connections, all indicated the invent-ion, reference being made to the acgenerally by the numeral I5, are shown for serving companying drawings thereof, wherein: the contactors, capacitors and coils. Common Figure 1 is a right side elevation, with some of cooling fluid conduits I6 are provided for the sevthe cover panels or doors removed and part of eral coils.

the coi1 hood cut away, of a three-coil furnace 55 A beam l1, here of I-section, extends above the entire furnace, that is, above all of the coils in whatever number provided, the beam being supported at its ends by end supports I3. each side of the beam l1 there is hinged one or more coil hood members i9 which may be closed, as shown in Fig. l, or opened, as shown in 2.

Aside from the main frame H, the bus bars l5, the beam Il, and the hoods I9, the apparatus has no parts which extend between units except control circuit wiring, and the self-contained. and identical heating units comprising coil, capacitors, contactors and related parts may be readily assembled in any desired number.V

In each unit the coil i2 is mounted as a removable unit on insulating end support plates 2i cured to ixed adjustablebus connections 213, a" l l each unit also carries coolingfluid manifolds which are disconnectible at hose connections 23 leading to the long fluid conduits it.

As shown in Figs. 4, 8, 9- andy 10, each heating coil is provided with stock supporting and guide rails 29 which project out of each end to such distance that in the open space between coils, the rails are veryclosetogether to form, in effect, continuous surfaces over which the work may mo've. However, the rails of adjacent coils can move laterally relative to each other so as not to interfere with the movement of a coil when being removed or replaced. The details of the guide rails and associated parts'will be described later. In this particular, the present application is a continuation-impart of the anplication of Harold A. Strickland, Jr., Serial No. 681,996, filed July 8, 1946, now Patent No. 2,541,123.

At the front end of the furnace, another cabinet Id is provided to house apparatus of a general nature which serves all coils in common, the apparatus here shown, Fig. l, comprising transformers 3| and operating pressure uid pumping and controlling apparatus 32.

The extreme front cabinet 19e houses the timers, switchboard, switches, relays, and other control apparatus. Some ofthe controls are mounted on a panel 33 on the side at the front where they will be accessible to an operator when in his usual position for feeding workpieces or billets to the machine.

The cabinets |911 and lle and their equipment are provided for all furnaces, whether assembled as one-coil heaters'or as multi-coil heaters.

Mounted upon the top of the cabinets lvd and ille is a work-feed unit 35 which is movable axially of the furnace upon guides 36 and is adjusted as a unit by a screw 31 threaded into a sleeve 38 mounted on the feed unit. The screw is rotatable but held against endwise movement in a support bearing 39 and is turnedz by a crank'40.

The feed mechanism comprises spaced end supports 42 which are permanently secured a-ta xed distance apart on a base 43 which slides on the guides 36.

fixed spaced relation by an inclined chute sup'- port piece 44 and an upper cross bar 45 which is' held in vertically adjusted positions on the end supports byY set screws 49. Chute guides 41 are adjustably secured to the support piece 44 by set screws 48 to provide for billets or workpieces W- of different lengths. At the upper end the chute guides are further held in adjusted positions by a slottedpiece 49 and set screws 50. The

The 'end supports are further held d upper cross bar carries a clamp device 5l for clamping billets in the chute and the vertical adjustment of the cross bar accommodates for billets of different thicknesses.

The support piece 44 has mounted thereon a gate device 53 which controls the downfeed of billets to loading position. ABoth the-clamp device 5| and the gate device 53 are here formed as cylinder-piston devices operated by pressure Huid;

VFrom the chute a'billet, when released by the opening of the gate53, falls upon a V-shaped feed trough 54 which is adjustably held on a cross piece 55 'by bolts 55 so as to be adjustable endwise to'staiid close to the projecting rails of the #l coil. When the feed device is adjusted-the trough is readjusted to bring it near the furnace rails. The V-trough plates are slotted from their ends to avoid inductance from the furnace coil.

A pusher device 8D, comprising piston and cylinder parts and a ram 6I, is mounted on theA outer end plate 42, as by a ring 52. On one side the ram carries a valve cam bar 53 having a cam G4 for operating the stems of a clamp valve CV and a gate valveGV respectively. The valve devices are mounted on a support bracket carried by an end plate 42.

A switch plate 66, hinged at 51' (Fig. 5), has its lower end located where it will be raised by a billet in the lowermost position just above theV gate plate 58. The upper end of the switch plate, when raised by the dropping ofthe lower end, operates micro-switches W-l, W-2, later to be described. y

The valve cam bar 53, when the piston is at the forward end of its stroke, operates a switch actuator 69 for switches RS-I and RS-Z which will be described later.

The exit or delivery end of the furnace beyond the rear end of the last heating coil has means for supporting a workpiece for a pause period to allow heat to penetrate toward the center. The billets heat so rapidly on the outside by induction that this soaking time is useful in preparing the workpiece for forging. As a matter of fact,`

the spaces between adjacent coils also provide a soaking time. It is to be understood that the current characteristics will be. chosen so as. to bestserve the conditions imposed, for example, a single coil furnace heating more deeply than a multi-coil furnace, but there is usually some need for a soaking time.

Surrounding the furnace exit and covering what may be termed a soaking chamber, there is provided a heat insulated hood 15 which comprises a metal casing 19 and a heat insulating lining 11. The hood is supported for swinging movement ona Vertical' axis on one side of the furnace by hinges 18 and is held in Vclosed position by a latch pin 19 on the other side.

At the bottom, the hood is provided with swinging doors 39, which may be referred'to as bomb bay doors, these being mounted on hinge shafts 8l in bearing brackets 82 and being urged to' closed position, as by a spring 83 secured between arms 84 carried by the door shafts 8l. When' a workpiece is pushed out from the soaking chamber, it drops upon the doors to open them and' pass through them, whereupon the spring 83l causes the doors to close again. At the end of the furnace and in line with its chamber axis, the hood 15 is provided with a transparencycovered sight opening 89. Another sight' open'- ing 81` is provided in the top of the hood. A billet deiiector 88 is provided in the top of the hood to cause an end billet to break away from the next billet in case they may be slightly fused together. At the sight opening 81 or at some other location in the hood, a heat or light responsive device, which may be referred to as an electric eye or photo relay, is provided to control the temperature `of the emerging billets, more particularly to shut oiT the heat if billets are near the melting point to endanger the heating coils. This device is indicated only in the wiring diagram where it is designated as PR.

In the coil hoods I9 there are provided vent openings 89 above the open space between coils to release heat, gases or smoke from the billets resting in the space between coils. It will be noted from Figs. 4, 8, 9 and 10, that the guide rails 29 are tubular and are cooled by fluid from disconnectible feed and return lines at one end. The cooling tubes are returned outwardly as at 90 at one end and have an outer run 9| which is located within the confines of the coil insulating lining 92 to keep it and the heating coil cool. The double rail construction with interconnecting supports 93 also provides strength for holding the insulation in place. The cooling rails are-mounted on the coil end plates 2| by bolts 94, 95 and adjustable connectors 96. It will be noted that the line-connected ends of the rails are returned through a coil support plate 2| and have their line connections above the outside of the coil and between its supporting plates, where there will be protection from heat. The inner run of the cooling rail is coated with a wear-resisting liner fused thereon. There are a number of suitable materials, one such being a composition of tungsten 12-17 chromiiun 30-35%, carbon 2.25-2.'75%, cobalt, substantially the balance, this being known commercially as Stellita The outer run 9| is provided with wings 91 which are fused thereon to hold the heat insulating lining of the coil.

For such coils or portions of coils as are subject to unusual heat from billets after they have been heated to high temperature, there is provided a special heat dissipating means, for example, of the type shown in Figs. 8, 9 and 10. Here an extensive mea of a highly heat conductive material, such as copper, is soldered to the outer run 9| of the rails so as to lie outside the heat insulation and inside the coil lining. The fins or plates 98 thus provided are slitted as at 99 to avoid buckling or other objectionable features of continuous sheets for such a use. It is found that if the heat shields are coextensive with the last approximately one-fth of the total heating coil length, they will provide adequate coil protection and prolong coil life to a remarkable degree.

y Between the ends of adjacent coils, inclined plates |02 may be provided for directing scale and dirt toward the outside of the cabinet assembly, the plates being supported upon brackets |03 on the coil end plates 2 I.

The operation of the apparatus will be described in connection with the circuit diagram, Fig. 11.

The ram 6| normally stops in its forward position,.that is toward the rear end of the machine as a whole. It is shown slightly back of forward position to illustrate its switches RS-l and RS-Z in their non-operated position. In the normal full forward stopped position of the ram,

its switch RS-I is closed and its switch RS-Z is open. RS--I opens and RS-Z closes as soon as the ram starts to move back.

A ram pause timer T| causes the ram to rest at the front end of its stroke. It is settable for a wide range of time merely by moving a xed contact hand which is engaged after the predetermined time lapse by a movable hand driven by a synchronous motor. This represents one form of timer which may be used. The end of the preset timer period is registered by closure of its switch T|-I. Its motor is represented by the reference character Ti-M. By providing the pause timer Tl, a number of control advantages are obtained, including the ability to adjust for different feed rates for billets of different size, different coils, different heats desired, and matching of delivery periods to suit the needs of the forging machines which use the billets heated by this machine.

The ram cylinder is provided with a valve RV operated by solenoid SO2. The arrangement is such that when the solenoid SO2 is not energized, the ram stays in its forward position and when the solenoid is energized, the ram returns to its rear position.

The ram cam bar 63, which carries the cam 64 for operating the valves CV and GV for the clamp 5| and gate 53 respectively, is shown also in Fig. ll. As the ram approaches the rear end of its travel, the associated valve CV causes the clamp 5| to hold the billet which is in next to last position. Later, near the rear end or" the ram travel, the associated valve GV causes the gate to be lowered to drop the billet from last position to the V-trough 54. When the ram moves forward again, it nrst replaces the gate in the chute and later releases the clamp to allow the stack of billets in the chute to slide down against the gate.

When the billet in last position drops, it opens switches W-l and 'yV-2, and when another billet drops to the last position, it closes these switches. If no billet drops down, the machine is stopped after a certain lapse of time. Whenever TR3 or TR2 becomes deenergized, the auxiliary switches open immediately.

To prepare for the start of operations, the main line switch S-| of Li, L2 is closed. For heating, as well as ram operation, a switch SM2, which may be referred to as a safe run switch, is closed. For operation of the ram only, S-Z is left open. The cooling water for the coils is turned on. This closes water shut-off valve switch VS, pressure switch PS and ilow switches FS to the coils (three here). The temperature at the coils is assumed to be not excessive so temperature switches TS are closed. The panels or doors of the cabinet are closed so their safety switches DS are closed. The hoods are closed so hood safety switches HS are closed. The rain is to be actuated and not held to a rear position so the ram return switch S-S is opened.

The clutch coil TZ-C of water shut-off delay timer T2 is kept energized as long as S-I is kept closed. It holds out the timer clutch but when S-l is opened, the clutch is engaged and after a time delay period, the timer switch is actuated to actuate solenoid SO to shut off water to bypass i supplying the heating coils. The synchronous motor for T2 is designated as T2M.

A time-delay relay Tltlv is energized and after a delay to allow bubbles to be removed from the cooling uid lines, its switch TRi-i is closed. The circuit involved is: Li, conductor |94,

atraveo 'lt-C, conductor 1115 ,l PS, VS, conductor 10S-a, to L2.

The-.ftime-delayv relays are represented oy separate: coilsv` for instantaneous and delay switch operation,V and the delay switch is, represented as carrying hinged vanes which ca-n fold. together move rapidly.- irr a iiuid in one direction of movement.A but. which spread and cau-se slow movement in the other direction. This is merely symbolic. Delay-action timers which are set-- table for timed periods of any predetermined length are available onthe market.

Itwillbe assumed that. the photo-electric rela PR will be used in. the soaking' chamber to. indi.- cate. when billets are. overheated. 'its switch PR--t isinl series, with the door and hood safety switches` DS. and HS.

Tostart operations, thev start pushioutton PB- is pressed to close PB-l and PIB-2.v

Closure of EBF-1 energizes relay R1. and the relay locksV in on itsswitch Rl-4. The circuit completed here is: L1, conductor 1&6, coillRl-C, conductor. 1..'|,.PB -i, conductor 108, stop push button switch FB2-l, conductor mt, to L2. Closure of Rlshorts out lill, PB-l and |33. RI also closes R|| in the line to heat pilot relay R3 but this has no eiect as yet because thev circuit is open elsewhere. The circuit in Vclved is: L1, conductor Ht, R3-C, conductor 1H, PR-|, DS, HS, conductor 112, R|-i, conductor' |13, conductor 114, conductor. H5, to

R3-I, which is open (or from H3 to conductor 116 and' PB-2 which also leads to open points). R1 also closes R1-2 to connect the ram pause timer relay Ti to L2. The circuit involved is: L1, conductor 11'1, conductor 113, Tl-M, conductor 1-19, R1--2, conductor 12?., to L2. The closure of PB-2 has no efect at this time as the circuit is open at both TR2 and TR3.

When the ram is fully at front end of its stroke, its switch RS-Iv is closedv and` Pts-2 opened.

RS-1, being closed, timer Tl is set into action and' after a timed period, the ram pilot relay R2 is energized. The circuit involved is: L1, conductor |23, R2--C, conductor |24, W-I (now closed), conductor |25.,- RS|, conductor 1243', conductor 127;.T1-1, H9, R1-2, 122,150 L2.

Energization of R2. closes its switch R12-2 which locks it in circuit and only the opening; ot W-1 or'Rl-d will deenergize it. It also cioses R2-1 which energizes ram valve solenoid SO2. and supplies fluid to the rod end of the ram cylinder and the ram retracts. The lock circuit is: L1, |23. RZ-C, 124, W-I, conductor 128. The circuit involved to energize S02 is: L1, conductor |29, SO2, conductor 133, R2-1, conductor- 131, to L2.

At the same time, timer TI energizes time delay relay TR3. The'circuit involved is: L1, Hl, conductor |33, TR3-C2, TR3-CLv conductor |34, |27, 'T1- 1, |,iSR|-2, 12E, toL2,

When ram starts to retract, it opens RS-i and closes RS-2.

Closure of RS2 puts TR3 directly in circuit where it will stay until RS-2 is again opened when the ram is at the forward end of its stroke again. The short or lock circuit for. TR3 is: TR3-CL 13%, 123, EES-2. conductor` |35, to L2.

Energization of TR3 opens TR3-2 and closes TR3-3. TR3-1 delays in opening, being timed to open after the ram has returned and the gate has opened and closed.

As the ram approaches the rearV end of' its stroke, its cam bar causes clamp valve CV to be actuated to clamp a billet in the next to last "if REL-2, R5-4, actuates the #2 contactors Aand .ril

TR2-1., 143, |152, TR1-1 etc.,v to L2.

closes R3-2 to the contactor relay circuits.

closed, close #I strokeit opens the gate to feed down a billet upon.

the guide.

Dropping down of a billet from the last-position opens switches W--I and W-2.

l Opening of W-1 deenergizes R2 and causes the. ram to move forward. It should here be noted that` when the machine was energized by closing S-I, and assuming aY billet to be in the last or feed-down position to keep W-2 closed, a timedelay relay TR2 will at once be energized and will be kept energized as long as W-Z is kept closed. The circuit involved is: L1, conductor |31, TR2-C2., TR2-C1, conductor |38, W-2, conductor. 1.39, toL2. Opening of W2 deenergizes` TR2' and causes it to open TR2-2 and close. TR2-1 both. without delay.

Asthe ram moves forward, its cam bar first causes the gate to close the bottom end of the chute andlater causes the clamp to release its billet tov allow the whole stack to descend. The loweimost billet closes switches W-l and W`-2'.

Closure of W-l has no immediate effect but. the closure of W-2 energizes TR2 again.

It will be assumed that the time-delay relay TR1 will have closed its switch TR1-1 completing a line to one side each of TR2-1 and TR3-l. The line established is as follows: L2, 105cv., VS., PS, TS, FS, conductor 141, TR1-1, conductor |42', 14'3 to TR2- 1, and 1M to TR3-1.

Energization of TR2 closes TR2-2 at once and begins a timing period for TR2-1 to open. It is set to open after the ram has moved forward' and paused at the outer end for its preset waiting period'.

The closed condition of both switches of TR2 has noimmediate effect because TR3" is still energized and TR3-2 is closed and TR3-1 not yet timed out if set properly.

./itend of its forward' stroke, the ram closes RS I and opens RS-Z.

- Opening of RS-Z deenergizes TR3 and this closes TR3-1 and TR3-2 and opens TR3-3, all withoutV delay.

Closure ofi TR32 (TR2-2 and TR2- 1 being closed) energizes the heat pilot relay R3. The circuit involved isz. L1, RS-C, H1, PR---1,k DS, HS, 1.12, R|-1,. H3, 114, conductor' |46, TR3-2., conductor 14.71, conductor 148, TR2-2, TR2- 1, 1333:, |42, TR1-1, 141, FS, TS, PS, VS, 135m, to L2.

Closure of R3-2 energizes #1 contactor relay R4 which closes the switches Ril- 1, R11- 2 and R-A of the #Il contactors and these, when contactor interlocks C|-1, Y The circuit involved. in energizing R4 is: L branchv conductor LBI conductor |52, R11-C, conductor |53, switch S-l (which is here closed on itsf normal contacts but which may be changed from |53 to an alternate route 154 to aV switch Rl-L. in brief the shift of S-li to 154 ksnorting out Re), conductorl |55, conductor 156, R3-2, conductor 157, S-2, conductor 158, LBZ, to L2.

Closure of. C1-1 and C1-2 energizes TRA which, after a delay period, closes TRIS- 1... The

circuit involved is: LBl, conductor. |60, TR-C (pilot-lamp 161 in parallel) conductor 162, C1-2'. (3i-l, conductor 163, to LB2.

Closure of TRll-Iv energizes #2 contactor relay R5 which, through its switches R5|,

these, when closed, close #2 contactor interlocks C2| and (E2-2. The circuit involved to energize R is: LBI, conductor |65, R5-C, conductor |66, S--5 (closed from |68 to |66 but shiftable when desired to |61 to cut out R5 to |61), conductor |68 (connected by conductor |69 to |54 of S-4), TR4-I, conductor |10, conductor |1|, |56, R3--2, |51, S-2, |58, to LB2.

Closure of C2| and C2--2 energizes TRS, which, after a delay period, closes TR5--|. circuit involved is: LBI, conductor |12, TRS- C (pilot lamp |13 in parallel), conductor |14, C2-2, CZ-I, conductor |15, to LB2.

Closure of TRE-l energizes #3 contactor relay R6 which, through its switches R6-|, R6-2, R6-4, actuates the #3 contactors and these, when closed, close #3 contactor interlocks C3 and C3--2. The circuit involved to energize R6 is LBI, conductor |11, R6-C, conductor |18, S-6 (closed to |18 but shiftable to open), conductor |19 (connected by conductor |80 to |61 of S-5), TR'i-l, conductor |8|, |1|, |56, R3-2, |51, S-2, |58, to LB2.

Closure of C3| and C3-2 energizes TRS which, after a delay period, closes TRS- i.

(pilot lamp 84 in parallel) conductor |65, C3-2, C3--|, conductor |86, to LB2.

Closure of TR6-| energizes relay R1. The circuit involved is: LBI, conductor |88, R1-C, conductor |89, TRS-I, conductor |90, |1|, |56, R3-2, |51, S-2, |58, to LB2.

Heat is thus placed successively on all three heating coils.

If the heat goes off and remains off for less than a predetermined period and R3-2 is closed, this will find the delay switch TRS-I closed and this will cause R1 to be energized which immediately closes Rl-l, R1-2 to supply current to the #2 and #3 coils. R3-2 causes current to be supplied to coil #I so all coils will be energized at one time. The circuit involved to supply current to the #2 coil is as follows: LBI, |65, R5-C, |66, S-5, |68, |69, |54, conductor |92, R1|, conductor |93, conductor |64, |1|, |56, R3-2, |51, S-2, |58, to LB2; and for current to #3 coil is as follows: LBI, |11, R6-C, |18, S-6, |19, |80, conductor |96, R1-2, conductor |91, conductor |98, |1|, |56, R3-2, |51, S-2, |58, to LB2.

At the end of the waiting period, the timer TI energizes ram pilot relay R2 to cause the ram to return, as before. It also energizes as before.

Energization of TRB closes TRB-3 and leaves TRB-l closed (until later opened) so heat pilot relay R3 is held in when TR2-l shortly opens. If TR2- opens first, R3 will be deenergized to open R3-i so that the later closure of TRS 3 will be ineffective to keep the heat on. However, operation of PB-Z would restore heat.

Similarly if TRS-l opens (as it should shortly after the gate closes) before TR2-2 closes when the gate closes, R3 will be deenergized and closure of TR2- 2 (TRS still being energized and TRS-2 open) will not energize R3. Again, closure of PB-Z would apply heat.

Hence, this allows the operator to put in billets and start the heat again without waiting.

The failure of W-l to close again after the last billet is fed down would prevent the ram from being returned from the outer end of its stroke.

The insertion of billets in the chute closes W-I and W-2 and causes the ram to start operating again.

The

Thek circuit involved is: LBl, conductor |83, TRS-C The heat contactor circuits are of known type and it is here only necessary to know that there are two contactors for each coil and that they supply the coils with high frequency current, derived from an independent source, by way of conductors 200, 26| for coil #L 202, 203 for coil #2, and 204, 205 for coil #3. Suitable control of multi-coil furnaces may be provided by using a transformer for one coil only, for example, coil #i as illustrated.

A solenoid MSO is provided for starting the hydraulic pump motor when current is turned Ion at S-I, overload devices OL being provided in connection therewith.

A pilot lamp 261 indicates when the switch S-l is closed.

The timing of operations will be clearer from consideration of Fig. ll, showing the cycle diagram. The duration of one complete cycle is represented by the top horizontal line 2|0 which extends between the vertical start line 2|| and the vertical finish line 2|2. The second horizontal line 2| 3 represents the ram movements. It starts back at line 2| and completes its backstroke at a vertical line 2|4. It starts again at the vertical line 2|5 and completes its forward stroke at the vertical line 2 I6. The ram. waits at the forward end of its stroke, as represented by the distance between the lines 2 I6 and 2 l2. The third horizontal line 2|1 represents the gate operation, which opens approximately at the line 2|4 to feed down a billet, and closes approximately at the line 2|5.

The horizontal line 2|8 represents the action of time-delay relay TRS. It is energized at ordinate 2H and deenergized at the line 2|6 but its time-delay switch TRB-I is set for actuation at a point 2 i5@ which is `a short time after the .ram is supposed to start forward. Hence, if there is any liam in the ram return or in the billet feed, the heating current will be shut off. If there is no workpiece or billet in the feed-down position to close switches W-l, W-2, the ram also wiil stop when it reaches the front end of its stroke, assuming that the ram did not jam on its backstroke but merely failed to get back on time.

rIhe line 2|9 represents the action of timedelay relay TR2. It is energized at the ordinate 2|5 where the ram starts forward and remains energized until the ram returns. Its switch TR2-I, however, is timed for actuation at the point 2| Ict which is slightly after the ram is scheduled to start its reurn movement. Hence. if there is any jam in the forward movement of the ram or if the proper pause at the front end of the ram stroke has not been observed, the heating current is cut oif.

To make the original setting, it is only necessary to place the movable contact element of the relay at a point some distance beyond the point required by the operations to be matched and supervised and then gradually to move the contact back until only a slight margin of Safety is left. In this way the supervisory response may be made as :fine or coarse as may be desired.

It is thus seen that the invention provides a furnace having improved feed means, improved work support and guide means, improved coil mounting and access, improved heat shield means for coils, improved exit enclosing means, and various other advantageous improvements.

While one embodiment has been described for purposes of illustration, it is to be understood that there may be various embodiments within 11 the limits of the `prior art and the 'scope of the fsub'joined claims.

I claim:

l. .An electric heating furnace comprising an .induction heating coil, workpiece guide rails with-in said coil, refractory lining outside said Arails within Vthe coil, a cooling tube nearer said coil than said rails, and a 'heat shield of extenlsive area thermally connected to said tube Within said coil, said shield being formed oi a material fof high heat conductivity.

`2. .An electric heating furnace comprising an induction heating coil, workpiece guide rails within said coil, refractory lining outside said iral's withn the coil, la cooling Atube nearer said coil than said rails, and a heat shield of extensive "area 'thermally connected to said tube within said coil, said vshield being formed of a mateial of high heat conductivity, said heat shields loein'g `serrated from their outer ends 'back "toward the cooling tube.

3. An electric heating v furnace comprising an induction heating coil, 'u'id cooled workpiece guide rails Wit-hin said coil, vsaid rails leach being turned at 'an end Vto .form a cooling tube which is :located nearer the y'coil than said rails and within velectrical insulating lining of :the coil, heat insulating lining Within said coil parthT supported on vsaid cooling tubes, and extensive 'heat shield fins secured to each tube Land extending lin opposite circumferential directions therefrom, Asaid lfms together 4forming Aa substantially cornplete circumferential lining for a, portion-at least -o'f said coil, said ns being slitted from `their ends 'back toward the cooling tubes.

HAROLD A. STRICKLAND, J R.

REFERENCES CITED The follow-ing kreferences are 'of -record lin vthe le of this patent:

UNITED STATES PATENTS Number Name Date 899,083 Taylor 4 Sept. 22, 1908 1,390,845 Tomlinson Sept. 113, 1921 1,431,997 lUnger Oct. .17, -1922 1,815,666 Cook et al July 21,I 1931 .1,861,869 Long vJune '7, 1932 .1,989,376 Northrup Jan. 29, 1935 2,005,901 .Long July .25, 1935 2,325,638 Strickland Aug. 3, '11.943 2,359,167 Somes Sept. A26, '1944 2,365,021 Strickland Dec. 12, 1944 v2,3!7-3,'7JJ9 .Strickland Apr. 157., 1945 l2,416,130 Treanor Feb. 18,., 1947 2,440,556 Paluev A131227, 1948 2,448,012 Baker Aug. .31, 1948 

